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path-util: fix path_is_mount_point() for symlinks

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path_is_mount_point() compares the mount_id of a directory and the
mount_id of the parent directory. When following symlinks, the function
to get the parent directory does not take the symlink into account.

/bin -> /usr/bin with /usr being a mountpoint:
mount_id of /bin with AT_SYMLINK_FOLLOW != mount_id of /
This commit is contained in:
Harald Hoyer 2015-02-20 13:25:42 +01:00 committed by Lennart Poettering
parent 918315e457
commit 27cc6f166b
1 changed files with 13 additions and 17 deletions
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30
src/shared/path-util.c
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@ -457,9 +457,9 @@ int path_is_mount_point(const char *t, bool allow_symlink) {
union file_handle_union h = FILE_HANDLE_INIT;
int mount_id = -1, mount_id_parent = -1;
_cleanup_free_ char *parent = NULL;
struct stat a, b;
int r;
_cleanup_close_ int fd = -1;
bool nosupp = false;
/* We are not actually interested in the file handles, but
@ -469,7 +469,15 @@ int path_is_mount_point(const char *t, bool allow_symlink) {
if (path_equal(t, "/"))
return 1;
r = name_to_handle_at(AT_FDCWD, t, &h.handle, &mount_id, allow_symlink ? AT_SYMLINK_FOLLOW : 0);
fd = openat(AT_FDCWD, t, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|(allow_symlink ? 0 : O_PATH));
if (fd < 0) {
if (errno == ENOENT)
return 0;
return -errno;
}
r = name_to_handle_at(fd, "", &h.handle, &mount_id, AT_EMPTY_PATH);
if (r < 0) {
if (errno == ENOSYS)
/* This kernel does not support name_to_handle_at()
@ -486,12 +494,9 @@ int path_is_mount_point(const char *t, bool allow_symlink) {
return -errno;
}
r = path_get_parent(t, &parent);
if (r < 0)
return r;
h.handle.handle_bytes = MAX_HANDLE_SZ;
r = name_to_handle_at(AT_FDCWD, parent, &h.handle, &mount_id_parent, AT_SYMLINK_FOLLOW);
r = name_to_handle_at(fd, "..", &h.handle, &mount_id_parent, 0);
if (r < 0)
if (errno == EOPNOTSUPP)
if (nosupp)
@ -510,10 +515,7 @@ int path_is_mount_point(const char *t, bool allow_symlink) {
return mount_id != mount_id_parent;
fallback:
if (allow_symlink)
r = stat(t, &a);
else
r = lstat(t, &a);
r = fstatat(fd, "", &a, AT_EMPTY_PATH);
if (r < 0) {
if (errno == ENOENT)
@ -522,14 +524,8 @@ fallback:
return -errno;
}
free(parent);
parent = NULL;
r = path_get_parent(t, &parent);
if (r < 0)
return r;
r = stat(parent, &b);
r = fstatat(fd, "..", &b, 0);
if (r < 0)
return -errno;